1. Field of the Invention
The present invention relates to a micro stepping motor, and particularly to an improved stepping motor of small size which utilizes a permanent magnet type rotor for positioning a magnetic head in a magnetic recording device.
2. Prior Art
There is well known a magnetic recording device which uses a magnetic disc as a recording medium. Recently, floppy disc has been currently used as such a magnetic disc. Floppy disc includes a flexible substrate and a magnetic layer formed thereon. The magnetic layer can electromagnetically store information of letters, numerals, symbols or figures so that the information will easily be written in and read from the floppy disc. Thus, the floppy disc is very useful as an external memory for various computers.
As well known, the magnetic disc is rotated on a spindle at a constant speed with tracks on the storing faces of the rotating floppy disc being adapted to store the desired information in a predetermined format. To write and read the information, a magnetic head is provided which is substantially radially movable relative to the magnetic disc. Thus, accuracy in positioning the magnetic head will directly influence the characteristics of storage in the system. If the accuracy is lower, Write/Read will not be carried out for a predetermined track in a proper format. Also, if there is any offset between the track and the magnetic head, that is, "off track", a serious malfunction will be produced.
Therefore, a stepping motor has been used to position the magnetic head with high accuracy. However, the stepping motor requires a complicated and relatively bulky structure which prevents the magnetic storage from being small-sized, as well known in the art.
Since floppy disc drives of smaller size and thickness have been utilized as magnetic storages in recent years, severe requirements of reduced size and improved accuracy are being made also relative to the stepping motor for positioning the magnetic head.